The invention relates to nuclear medicine, and more particularly relates to gantries for scintillation cameras. In its most immediate sense, the invention relates to scintillation camera gantries of the two detector (hereinafter, "dual-head") type.
A dual-head scintillation camera should provide the clinician with the option of conducting SPECT (Single Photon Emission Computed Tomography) studies with the detectors ("heads") in two configurations. In one configuration, the heads should be at 180.degree. with respect to each other while they rotate around the patient; in the other configuration, the heads should be at approximately 90.degree. with respect to each other while they rotate around the patient. This is because conventional SPECT studies are conducted with the heads opposed to each other, while cardiac SPECT studies are most efficiently carried out with the heads forming a right angle.
Systems of this general type are already known. For example, the VERTEX camera manufactured by ADAC Laboratories has two detectors which can be opposed to each other or can be angulated at an angle of less than 180.degree. with respect to each other while they rotate around the patient. However, known dual-head scintillation camera systems suffer from various disadvantages.
In particular, known dual-head scintillation camera gantries are insufficiently versatile and sometimes inconvenient to use. For example, the VERTEX camera is not well adapted to carry certain types of studies (e.g. studies in which the patient is standing or sitting). Additionally, it is difficult to transfer a patient from a gurney into the camera gantry.
It would be advantageous to provide a dual-head scintillation camera gantry which would permit the heads to be reconfigured between a 180.degree. configuration and a 90.degree. configuration, but which would nonetheless be able to carry out other types of studies (e.g. whole body bone scans).
It is accordingly one object of the present invention to provide a dual-head scintillation camera gantry which permits the heads to be reconfigured between 180.degree. and 90.degree. angulations and which also permits other types of studies to be carried out conveniently.
Another object of the invention is to provide such a gantry into which a patient can easily be transferred from a gurney.
Yet a further object of the invention is to provide such a gantry which is not only versatile but which can also be produced at reasonable cost.
Yet another object is, in general, to improve on known gantries of this general type.
In accordance with the invention, first and second scintillation camera detectors are provided and are mounted, respectively, to first and second yoke assemblies. The first yoke assembly is mounted to a ring gear which is rotatable within a vertical plane about a horizontal axis. The second yoke assembly is mounted to an annulus which is located within the ring gear and which is rotatable within the plane and about the axis. Means are provided for rotating the ring gear in said plane and about said axis and means are also provided for locking said first and second yoke assemblies together, whereby said first and second yoke assemblies rotate together when they are locked together and the first yoke assembly is being rotated by said rotating means.
Advantageously, and in accordance with the preferred embodiment of the invention, each detector is pivotally secured to its corresponding yoke assembly and each of the detectors is radially movable towards and away from the axis of the gantry. Furthermore, the entire gantry is laterally moveable.
A dual-head scintillation camera gantry in accordance with the invention is completely open along its axis. This permits whole body bone scans to be conducted by moving the patient axially while keeping the heads fixed. Additionally, by rotating the heads so their directions of view face parallel to the axis, sitting-patient studies can be conducted by placing the patient in front of one of the heads and keeping the gantry fixed in position. In SPECT studies where the heads do not orbit circularly with respect to the patient axis (so-called NCO or Non-Circular Orbit studies), the NCO feature can be conveniently accomplished by moving the patient up and down and/or moving the gantry laterally while the heads rotate around the patient. This has the advantage that a patient remains laterally fixed in position during the study. The patient is therefore less likely to be disoriented or disturbed by movement during the study.
In accordance with the invention, only one motor drive is required to accomplish the functions of head reconfiguration and head rotation. This reduces the standard cost of the resulting gantry. Furthermore, because the second yoke assembly is mounted to an annulus located within the first yoke assembly, a single-head scintillation camera gantry can be produced merely by omitting various parts and making only minor modifications to the gantry structure. In other words, the invention constitutes an easily-modified platform which may be used "as is" for a dual-head gantry or modified to produce a single-head gantry.